The present invention relates to an apparatus for simulating the friction of a material passing over human skin by performing an in vitro test without human skin. More specifically, this invention relates to an apparatus incorporating a simulated human tissue having a synthetic sheet and a porous layer which simulate the properties of human skin, including frictional resistance.
Friction is an important measure in the field of personal care products, such as facial tissue, bath tissue and baby wipes and for any product that contacts human skin during use. As friction between human skin and a product increases, the likelihood of causing damage to the skin increases. Further, determining the frictional properties of a particular product yields information about the way the product will feel on skin during use.
In the past, determining the coefficient of friction of a particular product on human skin required a friction test on a human subject. Experimentation on human subjects limits the potential number and variety of tests which may be administered. Moreover, tests requiring the use of unpleasant soiling agents or potentially uncomfortable products are difficult, if not impossible, to administer. Previous attempts to correlate in vitro testing to in vivo testing using a synthetic sheet or an organic skin have been generally unsuccessful. For example, silicone sheet as a substitute for human skin does not provide a proper correlation. Organic skins, such as porcine skin and snake skin, have also been tested as substitutes for human skin, without success. As such, there is a need for a test which will yield accurate friction measurements, without the need for an abundant supply of human subjects for testing. Because of the limitations of testing on human subjects, a substitute for human skin, which performs like human skin in friction coefficient testing, is needed.
Briefly, the present invention includes an in vitro testing method for predicting a coefficient of friction exhibited by a material passed over human skin, in vivo. A material is operatively connected between a scaffold and a load cell and a synthetic sheet is mounted on the scaffold. A porous layer is applied to an exposed surface of the synthetic sheet to form a simulated human tissue. The material engages the simulated human tissue. The method further comprises moving the material relative to the scaffold thereby to measure the coefficient of friction between the material and the simulated human tissue with the load cell.
In another aspect, the invention includes a simulated human tissue for evaluating the coefficient of friction between a material and the simulated human tissue to approximate the coefficient of friction that would be developed between the material and natural human skin.
In yet another aspect, the present invention includes a testing apparatus for evaluating a coefficient of friction. The testing apparatus comprises a scaffold sized and shaped to simulate a portion of human anatomy, a synthetic sheet and a load cell.
Other features of the present invention will be in part apparent and in part pointed out hereinafter.